1. Field of the Invention
This invention relates to a machine tool provided with a tool magazine for accommodating a plurality of tools and having a tool feeding function of selectively feeding one of the tools to a tool ejecting section of the tool magazine.
2. Description of the Related Art
Machine tool have conventionally been provided which include a tool magazine for accommodating a plurality of tools and have a tool selecting and moving function of selecting and moving one of the tools designated by an DC program to a tool ejecting section of the tool magazine. In these machine tools, when the tool selected and moved to the tool ejecting section has been attached to a spindle, the selection and movement of another tool designated by the MC program is initiated. In the tool selection, the tool is moved or fed to the tool ejecting section independent of a machining operation performed by the machine tool.
Accordingly, the tool selection and movement in sometimes carried out during execution of a machining operation requiring high precision according to a machining command designated by the MC program. The machining operation requiring the high precision includes cutting with movement in which a tool cuts workpiece while the workpiece in being moved. As a result, vibration or oscillation produced in the tool selection adversely affects the high-precision machining operation, thereby reducing the machining precision of workpiece.
To prevent the reduction in the machining precision, the inventors proposed an arrangement for controlling the machine tool so that the tool selection is not performed during execution of the cutting with movement etc. However, most of a machining time is consumed for the cutting with movement in machine tools requiring a high-speed machining. Accordingly, the tool selection can be performed only in a period between the time of completion of the cutting with movement and the time the tool is taken out of the tool magazine. Consequently, a time period required forth tool election results in a loss in the machining time.